COVID vaccines reduced the potential global death toll during the pandemic by almost two-thirds in their first year, saving an estimated 19.8 million lives, according to a mathematical modeling study yesterday in The Lancet Infectious Diseases.
An additional 600,000 lives could have been spared if a World Health Organization (WHO) goal of vaccinating 40% of the population of every country by the end of 2021 had been met, the authors of the study say.
Vaccination cut deaths an estimated 63%
To estimate the impact of vaccination worldwide, researchers from Imperial College London used a proven model of COVID-19 spread using country-level data for official COVID deaths that occurred from Dec 8, 2020—when vaccines were first rolled out—to Dec 8, 2021. They conducted a separate analysis of expected excess deaths to account for under-reporting of COVID-19 deaths during the study period.
They then compared the two analyses with a scenario that didn't include vaccination to arrive at their estimates. The data spanned 185 countries and territories.
The model accounted for variation in vaccination rates between countries, as well as differences in vaccine efficacy in each country based on efficacy data for various vaccines. They excluded China from their analysis because its strict lockdowns and large population would have skewed the results.
The scientists estimated that 18.1 million deaths would have occurred during the study period without vaccination. Of those, the model estimated that vaccination prevented 14.4 million deaths, or 79%. When they accounted for under-reporting, however, they found that COVID vaccination prevented an estimated 19.8 million deaths out of a total of 31.4 million potential deaths that would have occurred without vaccination—a reduction of 63%.
Of those prevented deaths, they estimated that 15.5 million (78.2%) were due to direct vaccine effects. The remainder were due to indirect vaccine affects through reduced disease transmission and lower burden on healthcare systems.
The authors found that high- and upper-middle-income countries accounted for the greatest number of prevented deaths (12.2 million), highlighting inequalities in vaccine access. And they estimated that an additional 599,300 deaths could have been averted if the WHO's target of vaccinating 40% of the population in every country by the end of 2021 had been met.
The authors conclude, "The results of this analysis still provide a comprehensive and thorough assessment of the impact of COVID-19 vaccination, revealing the substantial impact that vaccines have had and the millions of lives that are likely to have been saved during the first year of vaccination. Despite this, more lives could have been saved if vaccines had been distributed more rapidly to many parts of the world and if vaccine uptake could have been strengthened worldwide."
'More could have been done'
Lead author Oliver Watson, PhD, said in a Lancet news release, "Our findings offer the most complete assessment to date of the remarkable global impact that vaccination has had on the COVID-19 pandemic. Of the almost 20 million deaths estimated to have been prevented in the first year after vaccines were introduced, almost 7.5 million deaths were prevented in countries covered by the COVID-19 Vaccine Access initiative (COVAX).
"However, more could have been done. If the targets set out by the WHO had been achieved, we estimate that roughly 1 in 5 of the estimated lives lost due to COVID-19 in low-income countries could have been prevented."
Co-first author Gregory Barnsley, MSc, said, "Quantifying the impact that vaccination has made globally is challenging because access to vaccines varies between countries, as does our understanding of which COVID-19 variants have been circulating, with very limited genetic sequence data available for many countries. It is also not possible to directly measure how many deaths would have occurred without vaccinations. Mathematical modelling offers a useful tool for assessing alternative scenarios, which we can’t directly observe in real life."
In a commentary on the study in the same journal, Chad Wells, PhD, and Alison Galvani, PhD, of the Yale Center for Infectious Disease Modeling and Analysis, underscore various obstacles that countries faced in vaccinating their populations.
They note that the Democratic Republic of the Congo had to return more than 1.3 million donated doses and that more than 114,000 doses expired because of an inability to maintain cold-chain storage. They also highlight vaccine hesitancy caused by widespread misinformation in Nigeria and the United States and low vaccine uptake because of violence and unrest in Yemen and Ukraine.
"The saving of more than 19 million lives by the unprecedented rapidity of development and roll-out of COVID-19 vaccines is an extraordinary global health feat," Wells and Galvani write.
"Nonetheless, millions of additional lives could have been saved by more equitable distribution of vaccines. The most effective approaches to promote vaccination coverage worldwide are multifaceted… An enduring collective response is both pragmatic and ethically imperative."
